Display device having sealing grooves

ABSTRACT

A display device includes: a resin layer on the circuit layer including a groove surrounding and separating a display area; light-emitting elements on an upper surface of the resin layer so as to emit light with luminances controlled by the currents; a sealing layer covering the light-emitting elements; a second substrate above the sealing layer; a sealing material provided between the sealing layer and the second substrate so as to surround the display area and the groove; and a filling layer surrounded by the sealing material between the sealing layer and the second substrate. The groove is formed along a line describing a shape that is inscribed in a rectangle and not in contact with corners of the rectangle as viewed in a direction vertical to the upper surface of the resin layer.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese applicationJP2015-139217 filed on Jul. 10, 2015, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a display device in which alight-emitting element that is an electroluminescence (EL) element, anorganic EL element, or other self-luminous type display element ismounted.

2. Description of the Related Art

In a display device in which a plurality of light-emitting elementsrepresented by organic EL elements or the like are disposed, a displayarea is covered by a sealing layer configured of a silicon nitride filmor the like in order to prevent the degradation of the organic ELelements due to moisture entering the interior of the display device.

In JP 2008-186681 A, it is described to provide a highly reliableorganic EL display device capable of preventing degradation due to theinfluence of moisture. Especially in FIG. 2, an invention is disclosedin which, by coating a coating-type moisture absorbent in a directionaway from a corner portion of the display area, moisture or the like isprevented from entering from the corner portion of the display area.When the coating-type moisture absorbent is coated in the direction awayfrom the corner portion as described above, there is a problem in that apicture-frame area is increased.

Here, even when the light-emitting elements in the display area areprotected by the sealing layer, adverse effects due to the entry ofmoisture may occur.

A path for moisture to the display area protected by the sealing layeris assumed to be formed in a planarizing layer formed of an organicinsulating film for planarizing irregularities caused by a circuit layeror in a pixel separation film formed of an organic insulating film forseparating the light-emitting elements for each pixel.

SUMMARY OF THE INVENTION

In view of the problems described above, it is an object of theinvention to provide a display device in which the entry of moistureinto a display area where a plurality of light-emitting elements aredisposed is prevented.

A display device according to an aspect of the invention includes: afirst substrate; a circuit layer formed on the first substrate so as toinclude circuits for controlling currents respectively corresponding toa plurality of unit pixels constituting an image; a resin layer providedon the circuit layer and including a groove surrounding and separating adisplay area; a plurality of light-emitting elements provided on anupper surface of the resin layer so as to emit light with luminancescontrolled by the currents; a sealing layer covering the plurality oflight-emitting elements; a second substrate disposed above the sealinglayer; a sealing material provided between the sealing layer and thesecond substrate so as to surround the display area and the groove; anda filling layer surrounded by the sealing material between the sealinglayer and the second substrate, wherein the groove is formed along aline describing a shape that is inscribed in a rectangle and not incontact with corners of the rectangle as viewed in a direction verticalto the upper surface of the resin layer.

A display device according to another aspect of the invention includes:a first substrate; a circuit layer formed on the first substrate so asto include circuits for controlling currents respectively correspondingto a plurality of unit pixels constituting an image; a resin layerprovided on the circuit layer and including a groove surrounding andseparating a display area; a plurality of light-emitting elementsprovided on an upper surface of the resin layer so as to emit light withluminances controlled by the currents; a sealing layer covering theplurality of light-emitting elements; a second substrate having a planarshape smaller than that of the first substrate and disposed above thesealing layer so as to expose a portion of the first substrate; asealing material provided between the sealing layer and the secondsubstrate so as to surround the display area and the groove; and afilling layer surrounded by the sealing material between the sealinglayer and the second substrate, wherein the planar shape of the secondsubstrate includes corner portions that are inscribed in a rectangle andcoincident with or inside corners of the rectangle, and the groove isformed along a line describing a similar figure obtained by reducing ashape that is inscribed in the planar shape of the second substrate andnot in contact with the corner portions as viewed in a directionvertical to the upper surface of the resin layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an organic EL display device accordingto a first embodiment.

FIG. 2 is a schematic view showing the state of a pixel circuit of theorganic EL display device in the first embodiment.

FIG. 3 is a cross-sectional view for explaining the state of a pixel ofthe organic EL display device in the first embodiment.

FIG. 4 is a cross-sectional view for explaining the state of apicture-frame area located around the periphery of a display area andthe state of a terminal portion of the organic EL display device in thefirst embodiment.

FIG. 5A is a plan view showing the state of the vicinity of cornerportions of the display area in the first embodiment.

FIG. 5B is an enlarged plan view showing the state of the vicinity ofone corner portion of the display area in the first embodiment.

FIG. 5C is an enlarged plan view showing the state of the vicinity ofone corner portion of the display area in the first embodiment.

FIG. 6 is a diagram showing the state of a cross-section along VI-VI inFIG. 5A.

FIG. 7 is a diagram showing Modified Example 1 of the organic EL displaydevice in the first embodiment.

FIG. 8 is a diagram showing Modified Example 2 of the organic EL displaydevice in the first embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an organic EL display device according to each embodimentof the invention will be described with reference to the drawings.

First Embodiment

FIG. 11 is a schematic plan view for explaining an organic EL displaydevice 1 of a first embodiment. The organic EL display device 1 of theembodiment is configured by bonding a second substrate B2 to a firstsubstrate B1 on which organic electroluminescence elements as aplurality of light-emitting elements are disposed. In an area (exposedarea EX) of the first substrate B1 exposed from the second substrate B2,a driver semiconductor device IC for driving the organic EL displaydevice 1 is disposed. Further, a flexible printed board FPC is disposedin the vicinity of the edge portion of the exposed area EX of the firstsubstrate B1.

FIG. 2 is a diagram showing the state of a pixel circuit in a displayarea DP of the organic EL display device 1 of the first embodiment. Theorganic EL display device 1 includes the display area DP where an imageis displayed, a scanning signal line drive portion GDR, a video signalline drive portion DDR, and a power source drive portion EDR.

In the display area DP, organic electroluminescence elements OL andpixel circuits PX are disposed in a matrix corresponding respectively toa plurality of pixels. The pixel circuit PX is configured of a thin filmtransistor TFT1, a capacitive element CAP, and a thin film transistorTFT2. The scanning signal line drive portion GDR, the video signal linedrive portion DDR, and the power source drive portion EDR drive thepixel circuit PX to control light emission of the organicelectroluminescence element OL.

The scanning signal line drive portion GDR is connected to scanningsignal lines GL each provided for an array of pixels (pixel row) in thehorizontal direction, and outputs a scanning signal to the scanningsignal lines GL sequentially selected.

The video signal line drive portion DDR is connected to video signallines DL each provided for an array of pixels (pixel column) in thevertical direction, and outputs, in synchronization with the selectionof the scanning signal line GL by the scanning signal line drive portionGDR, a voltage in response to a video signal of the selected pixel rowto each of the video signal lines DL. The voltage is written to acapacitor in the pixel circuit PX, and a current in response to thewritten voltage is supplied to the organic electroluminescence elementOL.

The power source drive portion EDR is connected to drive power sourcelines SL each provided for the pixel column, and supplies a current tothe organic electroluminescence element OL through a switching elementin the pixel circuit PX.

A cathode of the organic electroluminescence element OL is connected toa ground potential, and the cathodes of the organic electroluminescenceelements OL of all of the pixels are configured of a common electrode.

FIG. 3 is a diagram for explaining the state of a cross-section of aunit pixel in the organic EL display device 1 of the first embodiment.As shown in the drawing, the organic EL display device 1 is configuredto include the first substrate B1 on which the plurality of organicelectroluminescence elements OL are formed, the second substrate B2which is disposed to face the first substrate B1 and on which a colorfilter layer CF and a black matrix BM are formed, and a filling layer FLfilled between the first substrate B1 and the second substrate B2.

Moreover, the organic electroluminescence element OL is configured toinclude a pixel electrode P1, an organic layer E1, and a commonelectrode C1, in which the pixel electrode P1 and the organic layer E1are in contact with each other and the organic layer E1 and the commonelectrode C1 are in contact with each other. A wiring layer L1 forforming the capacitive element CAP between the pixel electrode P1 andthe wiring layer L1, and a capacitive insulating layer CP are disposed.The capacitive insulating layer CP is formed of an inorganic insulatingfilm such as, for example, silicon nitride (SiNx). Moreover, aplanarizing layer (resin layer) HPL formed of an organic insulating filmsuch as acrylic resin or polyimide resin is formed for a base of theorganic electroluminescence element OL, and the pixels (the organicelectroluminescence elements OL) are separated from each other by a banklayer (resin layer) BNK formed of a similar organic insulating film.

The pixel electrode P1 (anode) of the organic electroluminescenceelement OL is formed of high-reflective metal such as aluminum, andextends to the bottom portion of a contact hole CH to be connected to atransparent conductive layer T1. The pixel electrode P1 is electricallycontinuous with a source electrode of the thin film transistor (TFT)formed below the planarizing layer HPL. The common electrode C1 isformed of a transparent conductive film such as indium tin oxide (ITO),and serves as one layer of solid-like electrode common to all of thepixels in the display area DP.

The organic layer E1 in the embodiment is formed between the commonelectrode C1 and the pixel electrode P1, and configured to include ahole transport layer, a light-emitting layer, and an electron transportlayer. In the light-emitting layer in the organic layer E1, holesinjected from the pixel electrode P1 and electrons injected from thecommon electrode C1 are recombined to emit light. All of the layersconstituting the organic layer E1 may be formed over the entire displayarea DP, or may be formed individually for each of the pixel. Theluminance of the light-emitting layer of the organic electroluminescenceelement OL is controlled by a current from a circuit layer CL. Thecircuit layer CL includes the thin film transistor TFT2 and the thinfilm transistor TFT1 (not shown).

Moreover, the organic electroluminescence elements OL of the pixels arecovered and protected by a sealing layer PR. The sealing layer PR in theembodiment is configured of an inorganic insulating film, andspecifically, configured to include a silicon nitride layer and asilicon oxide layer. The sealing layer PR may include, for example, aresin layer interposed partially between the silicon nitride layer andthe silicon oxide layer, or an organic insulating film may be includedin a portion of the sealing layer PR in some cases.

The planarizing layer HPL is formed of an organic insulating film to arelatively thick thickness, and absorbs steps produced on the circuitlayer CL in which the thin film transistor TFT and the like are formed,and planarizes the circuit layer CL. As shown in the drawing, thecircuit layer CL is configured to include the electrodes of the thinfilm transistor connected to the pixel electrode P1, other wirings, agate insulating film, and an inter-layer insulating film, and includescircuits for controlling currents respectively corresponding to thepixels in the display area DP.

FIG. 4 is a diagram showing the state of a picture-frame area locatedaround the periphery of the display area DP and the state of a terminalportion TE formed in the exposed area EX of the organic EL displaydevice 1 in the first embodiment. The left figure in FIG. 4 shows thestate of the picture-frame area, while the right figure shows the stateof the terminal portion TE. A sealing material DM that bonds the firstsubstrate B1 and the second substrate B2 together is providedtherebetween. The sealing material DM is disposed along the outline ofthe second substrate B2, and the filling layer FL is disposed inside thesealing material DM.

As shown in the left cross-sectional view in FIG. 4, the commonelectrode C1 is in contact with the transparent conductive film T1exposed in the picture-frame area (outside the display area DP), and issupplied with a common potential through the wiring layer L1. As shownin the right cross-sectional view in FIG. 4, a metal layer in the samelayer as the source/drain electrode of the thin film transistor isexposed in the terminal portion TE, and connected from the terminalportion TE to the driver semiconductor device IC.

Here, especially FIG. 5A shows a schematic view when the first substrateB1 of the organic EL display device 1 in the embodiment is viewed fromabove. As shown in the drawing, a groove GR1 (first groove) for blockingthe entry of moisture from the planarizing layer HPL and the bank layerBNK both formed of an organic insulating film is disposed between thedisplay area DP where an image is displayed and an area where thesealing material DM is disposed. FIGS. 5B and 5C are diagrams eachshowing an enlarged view of a corner portion at the upper right portionof the organic EL display device 1, in which representation of a grooveGR2 (second groove) is omitted.

The sealing material DM has a rounded shape at the corner portions ofthe second substrate B2 bonded to the first substrate B1, and includescurved portions CV each of which is concave in a direction in which thecorner portion of the display area DP projects. The groove GR1 isconfigured in such a shape to avoid overlapping with the sealingmaterial DM because an entry path for moisture to the display area DPmay be formed when the groove GR1 overlaps the sealing material DM. Thatis, as viewed planarly, the groove GR1 is formed, as shown in FIGS. 5Aand 5B, so as to be inscribed in a rectangle RC surrounding the displayarea DP, and formed, at the portions of corners of the rectangle, alonga line describing a shape that is not in contact with the corners.

From another point of view, as shown in FIG. 5C (representation of thegroove GR2 is omitted in FIG. 5C), the groove GR1 is formed along a linedescribing a similar figure SH1 to a shape SH that is inscribed in theplanar shape of the second substrate B2 and not in contact with thecorner portions of the second substrate B2, and formed to be smallerthan the shape SH.

Specifically, the groove GR1 in the embodiment extends in a straightline in an oblique direction inside the corners of the rectangle RCsurrounding the display area DP to connect the groove GR1 that extendsin the vertical direction with the groove GR1 that extends in thehorizontal direction, and thus the groove GR1 depicts chamfered cornerswith the vertices of the rectangle of the display area DP removed.

Although, in FIG. 5A, the groove GR2 is also formed at a positionoverlapping the sealing material DM, the groove GR2 may not benecessarily present in terms of blocking moisture.

FIG. 6 is a diagram showing a cross-section along VI-VI in FIG. 5A. Asshown in the drawing, the groove GR1 is formed by removing theplanarizing layer HPL and the bank layer BNK by etching. As describedabove, the groove GR1 divides the resin layers into the resin layers onthe display area DP side and the resin layers on the sealing material DMside.

As the groove GR1 in the embodiment, first, an outer tapered shape GRais formed in the planarizing layer HPL that is located around theperiphery of the display area DP and located in the picture-frame area.Further, the capacitive insulating layer CP is formed on the surface ofthe tapered shape GRa, so that the organic insulating film due to theplanarizing layer HPL is divided by the inorganic insulating film. Next,the bank layer BNK is formed so as to be filled in the tapered shape GRacovered by the capacitive insulating layer CP, and thereafter, an innertapered shape GRb is further formed. The common electrode C1 is formedon the surface of the inner tapered shape GRb, and further, the sealinglayer PR is filled inside the tapered shape GRb.

Hence, in the groove GR1, the organic insulating films of the bank layerBNK and the planarizing layer HPL are divided by the sealing layer PRand the common electrode C1, and further, the organic insulating film ofthe planarizing layer HPL is divided by the capacitive insulating filmCP. With the groove GR1 described above, a moisture path that may beformed in the bank layer BNK or the planarizing layer HPL is divided, sothat moisture is prevented from reaching the organic layer E1 formed inthe display area DP and thus the reliability of the organic EL displaydevice 1 is improved.

In the embodiment as described above, the groove GR1 is configured ofthe outer tapered shape GRa and the inner tapered shape GRb in theplanarizing layer HPL. However, it is sufficient that the groove GR1penetrates the organic insulating films of the planarizing layer HPL andthe like so as to reach the inorganic insulating film located on theuppermost surface of the circuit layer CL and in contact with the lowersurface of the planarizing layer HPL and, further, the planarizing layerHPL on the display area DP side and the planarizing layer HPL on theoutside thereof are divided with the inorganic insulating film thatintervenes therebetween.

Moreover, the groove GR2 surrounds the groove GR1 from the outside, andis formed into a rectangular shape. However, since the groove GR2 isformed at the position overlapping the sealing material DM, there is arisk that the sealing layer PR and the like within the groove GR1 may bebroken by spacer particles SP that are contained in the sealing materialDM and define a gap between the first substrate B1 and the secondsubstrate B2. For this reason, there is a possibility that an entry pathfor moisture is formed in the groove GR2, so that the groove GR2 alonecannot sufficiently prevent the entry of moisture into the display areaDP.

Moreover, when the groove GR1 is formed angular without removing thevertices of the rectangular shape similarly to the planar shape of thegroove GR2, there is a possibility that the rounded curved portion CV ofthe sealing material DM may overlap the groove GR1 at the position ofthe corner of the groove GR1 due to a slight shift in the disposition ofthe sealing material DM. As described above, when the overlapping of thesealing material DM and the groove GR1 occurs, there is the risk thatthe sealing layer PR may be broken by the spacer particles SP containedin the sealing material DM and thus the entry path for moisture may beproduced. Therefore, by forming the groove GR1 with a rectangular planarshape with the vertices removed as in the embodiment, the entry ofmoisture can be prevented while reducing alignment accuracy fordisposing the sealing material DM. Further, since there is no need tocoat a coating pattern of the sealing material DM in an outward convexshape so as to avoid the corner portion of the groove GR1, thepicture-frame area can be narrowed.

Next, FIG. 7 is a diagram showing Modified Example 1 of the organic ELdisplay device 1 of the first embodiment. As shown in the drawing, theplanar shape of the groove GR1 is formed so as to be inscribed in thetop, bottom, left, and right sides of the rectangle RC surrounding thedisplay area DP, while extending, inside the corners of the rectangleRC, in a curved line that is convex in the projecting direction of thecorners. Specifically, the groove GR1 of Modified Example 1 has arounded shape inside the corners surrounding the display area DP. Thecurvature of the corner portion in the groove GR1 may be larger than thecurvature of the corner portion of the sealing material DM.

By forming the corner portions in the groove GR1 into a rounded shape asdescribed above, a stress is prevented from concentrating on the sealinglayer PR and the like filled in the groove GR1, and thus the breakage ofthe sealing layer PR at the corner portion is prevented. The overlappingof the sealing material DM and the groove GR1 can also be prevented, andthus the breakage of the sealing layer PR at the corner portion isprevented.

FIG. 8 is a diagram showing Modified Example 2 of the organic EL displaydevice 1 of the first embodiment. As shown in the drawing, grooves GR3(third grooves) that couple the groove GR1 disposed inside the sealingmaterial DM with the groove GR2 disposed overlapping the sealingmaterial DM are formed in Modified Example 2. The grooves GR3 are formedwhile avoiding the corner portions of the groove GR2 and the like, sothat even when moisture enters the corner portion of the groove GR1, themoisture is prevented from traveling to the sides connected to thecorner portion of the groove GR1.

Although, in the embodiment described above, the inorganic insulatingfilm or the metal layer other than the sealing layer PR is also formedinside the groove GR1, the inorganic insulating film or the like otherthan the sealing layer PR may not be included for example. Moreover, thesealing layer PR may be configured of a single layer of inorganicinsulating layer, or may be configured of a plurality of different kindsof inorganic insulating layers.

The display device in the embodiment described above is the organic ELdisplay device 1, but is not limited to an organic EL display device aslong as it is a display device. The display device may be a displaydevice including a light-emitting element such as a quantum-dotlight-emitting diode (QLED) in each pixel.

While there have been described what are at present considered to becertain embodiments of the invention, it will be understood that variousmodifications may be made thereto, and it is intended that the appendedclaims cover all such modifications as fall within the true spirit andscope of the invention.

What is claimed is:
 1. A display device having a display region, thedisplay device comprising: a first substrate having an insulatingsurface; a circuit layer on the insulating surface, the circuit layerhaving a pixel circuit in the display region; a first insulating layercovering the circuit layer, the first insulating layer having a firstgroove and a second groove; a pixel electrode on the first insulatinglayer, the pixel electrode being connected to the pixel circuit; and asecond insulating layer on the first insulating layer, the secondinsulating layer having a third groove and a fourth groove, wherein thefirst groove surrounds the display region in a plan view, the secondgroove surrounds the display region, the first groove is between thedisplay region and the second groove in the plan view, the third grooveoverlaps with the first groove and inside the first groove, the fourthgroove overlaps with the second groove and inside the second groove, andboth edges of the first groove and both edges of the second groove arecovered with the second insulating layer.
 2. The display deviceaccording to claim 1, further comprising a light emitting element,wherein the light emitting element includes the pixel electrode, acommon electrode, and an organic layer including a light emittingmaterial between the pixel electrode and the common electrode, and thesecond insulating layer covers an edge of the pixel electrode andexposes a part of an upper surface of the pixel electrode.
 3. Thedisplay device according to claim 2, wherein the common electrode coversthe pixel electrode, the organic layer, first groove, and the thirdgroove, and the common electrode does not cover the second groove andthe fourth groove.
 4. The display device according to claim 1, furthercomprising a sealing layer, wherein the sealing layer covers the displayregion, the first groove, the second groove, the third groove, and thefourth groove continuously.
 5. The display device according to claim 1,wherein each of the first insulating layer and the second insulatinglayer comprises an organic insulating material.
 6. The display deviceaccording to claim 4, wherein the sealing layer comprises an inorganicinsulating material including silicon nitride.
 7. The display deviceaccording to claim 1, further comprising: a second substrate; and asealing material between the first substrate and the second substrate,wherein the sealing material surrounds the display region in the planview, the sealing material covers the second groove and the fourthgroove, and the sealing material does not cover the first groove and thethird groove.
 8. The display device according to claim 1, furthercomprising: a second substrate; and a filling material between the firstsubstrate and the second substrate, wherein the filling material coversthe display region, the first groove, and the third groove.